VOL. 23, NO. 24	JUNE 12, 1998

rug resistance of Mycobacterium tuberculosis, the bacterium that causes tuberculosis, is a global phenomenon. But it is worse in a number of recently identified “hot zones,” reports the World Health Organization—International Union Against Tuberculosis and Lung Disease Global Project on Anti-Tuberculosis Drug Resistance Surveillance, in the June 4 New England Journal of Medicine.

  The project surveyed an average of 555 patients in each of 35 nations, from 1994 to 1997, for resistance to any of four commonly used drugs. The study is the first to standardize surveys, surveillance reports, reporting methods, laboratory tests, and definitions used in describing the prevalence of this common infectious disease.

  “In the past, we had isolated reports, with no way to compare how many cases occurred in which nations. This study provides, for the first time, a global look at the prevalence of drug resistance to tuberculosis,” says Ariel Pablos-Mendez, M.D., M.P.H., an assistant professor of medicine and public health at Columbia’s College of Physicians & Surgeons and lead author of the study.

  The study reveals an uneven distribution of drug resistance to TB worldwide. Incidence was low in many countries, including the United States, Brazil, and several African nations, but elevated in the Dominican Republic, India, the former Soviet Union, and Argentina.

  “This is the first major report which confirms that TB “hot zones” are emerging around the world,” says Mario Raviglione, M.D., of the WHO and co-author of the report. “In these “hot zones,” multi-drug resistant TB is virtually incurable without expensive and sophisticated health care. The World Health Organization is taking a lead in coordinating international efforts to tackle this problem,” he adds.

  Bacteria naturally undergo mutations that create drug resistance, but these are rare events. When a patient does not take anti-tuberculosis drugs regularly, as prescribed, those rare resistant bacteria can persist. Not only does this selection for pre-existing drug-resistant variants complicate treating the patient in whom the problem originates, but then that person can transmit the resistant bacterial strain.